the.com/indian winter

means A stretch of unseasonably warm weather that arrives in late autumn or early winter, lulling everyone into believing the cold is over before it isn't.

from This is a lesser-used cousin of 'Indian summer,' a term that dates to 18th-century North America for a late warm spell after the first frosts. The origin of 'Indian' in that phrase is genuinely murky — old folk explanations (that Native peoples relied on this window for final harvests or hunts, or that it was first noticed in regions they inhabited) aren't confirmed by historical record, just popularly repeated guesses. 'Indian winter' simply extends the same naming logic to a later, colder-season false thaw, riding on the original phrase's pattern rather than any separate documented history of its own.